2021-08-18 12:35:03
The Sombrero Galaxy has attracted the attention of astronomers since its discovery in 1781. At that time it was thought to be one more nebula of those that abound in the Milky Way, but at the beginning of the last century it was discovered to be a huge formation with a mass of more than 800,000 million suns located at such a distance that its light takes 30 million years to reach us. The image offered to us by modern telescopes is truly spectacular, a bright elongated shape, with a large bulge in the center, crossed lengthwise by a dark band that divides it in two, which gives a slight appearance with a hat.
Beyond the spectacular images, scientists like David Martínez Delgado, a researcher at the IAA–CSIC and a guest in Talking to Scientists, search the sombrero galaxy for traces that reveal the very evolution of galaxies. In a recent article, published in the Monthly Notices of the Royal Astronomical Society, David and a diverse team of researchers reveal in detail a population of stars that are ordered to form a kind of stellar stream, a formation that has a common origin in a galaxy. minor that has been deformed and stretched by the tides caused by the gravity of the Sombrero galaxy.
The research published now is part of what we could call “galactic archaeology” because it looks for indications of events that happened in the past of these enormous concentrations of stars. Until now it is assumed that large galaxies such as the Milky Way, or the Sombrero Galaxy, were formed by the merger of many smaller galaxies that were thus increasing their mass until they formed the current enormous structures. In the process, the smaller galaxies are torn apart by the larger one and their stars scattered by galactic gravity in structures called “stellar tidal currents.”
However, it can also happen that this formation process suffers a significant boost when two large galaxies collide with each other and merge to form an even larger one. In this case, the remains of both contributors are mixed and must leave signs of their past in the current images. This is what is thought to have happened in the Sombrero galaxy, according to studies carried out on images obtained by the Hubble Space Telescope in 2020. Those studies revealed that, in the galactic halo, an extensive region enveloping the galaxy, is observe a large number of stars rich in metals, that is, in elements heavier than the primordial hydrogen or helium. This high metallicity indicates that these stars have formed recently, agglutinating material released by previous generations of stars. This discovery raised the hypothesis that the Sombrero galaxy would have undergone a kind of rejuvenation thanks to the large amounts of gas and dust provided by another large galaxy.
David Martinez Delgado and his team tried to verify this hypothesis by observing the galaxy with small robotic telescopes, commonly used by amateur astrophotographers to obtain impressive images of the sky, some of which are usually published in “NASA Astronomy Picture of the Day”. ”:https://apod.nasa.gov/apod/archivepix.html and gain worldwide fame. The results were not as expected. Instead of discovering the tidal currents coming from the hypothetical big collision, the researchers found another tidal current that completely envelops the galaxy’s disk and which, based on theoretical simulations, they have proven to belong to to the remains of a satellite dwarf galaxy that has been engulfed by the larger one.
The result of this research has been possible thanks to the images obtained by the astrophotographer Manuel Jiménez with an 18-centimeter robotic telescope, the contribution of David Malin, a researcher at the Australian Astronomical Observatory, and a large group of astrophysicists who have managed to extract the information about the tidal current of the whole image of the galaxy, .
I invite you to listen to David Martinez-Delgado Talentia Senior Fellow at the Instituto de Astrofísica de Andalucía (IAA–CSIC)
REFERENCES:
A feather on the hat: tracing the giant stellar stream around the Sombrero galaxy
David Martínez-Delgado, Javier Román, Denis Erkal, Mischa Schirmer, Santi Roca-Fàbrega, Seppo Laine, Giuseppe Donatiello, Manuel Jimenez, David Malin, Julio A Carballo-Bello. Monthly Notices of the Royal Astronomical Society, Volume 506, Issue 4, October 2021, Pages 5030–5038,
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